Longodus

Longodus Temporal range: Ludlow PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Agnatha
Subclass:	Thelodonti
Order:	Thelodontiformes
Family:	Longodidae Märss, 2006
Genus:	Longodus Märss, 2006
Species:	L. acicularis
Binomial name
Longodus acicularis Märss, 2006 [1]

Longodus (Long meaning long and odus meaning tooth) is an extinct genus of thelodont, placed in its own family[1][2] – Longodidae – which existed in what is now Estonia during the Ludlow epoch of the upper Silurian period.[3] The type and only species is Longodus acicularis.[1][3] They are most noted for their long, needle-like scales, which run vertically along their trunk.

Description

Longodus acicularis possessed narrow but elongated scales, approximately 0.5 mm to 1.0 mm in length, with a width to length ratio of up to 1:11. Their heads were almond shaped, connected to a medium trunk and short, distinctly forked tail. Scales contained ridges along the margins, creating a ripple like visual effect. They also possess lateral spines posterior to the crown.[2] The scales on the crown are dentine based, covered by enameloid, while the scales of the base are acellular aspidin based.

References

1. T. Märss (2006). "Thelodonts (Agnatha) from the basal beds of the Kuressaare Stage, Ludlow, Upper Silurian of Estonia" (PDF). Proceedings of the Estonian Academy of Sciences, Geology. 55 (1): 43–66. doi:10.3176/geol.2006.1.03. S2CID 199522655.
2. Mark V. H. Wilson & Tiiu Märss (2009). "Thelodont phylogeny revisited, with inclusion of key scale-based taxa" (PDF). Estonian Journal of Earth Sciences. 58 (4): 297–310. doi:10.3176/earth.2009.4.08.
3. Märss, T., Turner, S. & Karatajūte-Talimaa, V. 2007. "Thelodonti". In H.P. Schultze (ed.). Agnatha II (PDF). Vol. 1B. Verlag Dr. Friedrich Pfeil, München. p. 143.